Keithley 708A Instruction Manual Download

Page: 71 / 167

IEEE-488 Programming

5-7

5.7

Indicator and control aspects of IEEE-
488 operation

The following paragraphs discuss aspects of front panel indi-
cators and controls with respect to IEEE-488 operation,
including the error LED (ERR), IEEE-488 status indicators,
and the LOCAL key.

5.7.1 Error LED

The Model 708A monitors a number of operations associ-
ated with IEEE-488 programming. If an error is found, the
Model 708A lights an error LED (ERR). Program the Model
708A to generate an SRQ (paragraph 5.9.12), and then the
U1 error status word (paragraph 5.9.20) can be checked for
specific error conditions.

The following paragraphs describe conditions (associated
with IEEE-488 programming) causing the front panel ERR
LED to illuminate.

Card identification error

A card ID error occurs when the instrument's power-up rou-
tine detects a checksum error in the information from a card.
When in master/slave configuration, the cards in error are
indicated by all LEDs in their crosspoint display blocks
being lit.

IDDC (illegal device-dependent command) error

An IDDC error occurs when the unit receives an illegal
device-dependent command over the bus. For example, the
command string 1X includes an illegal command because
the “1” is not part of the instrument's programming language.

NOTE

When an IDDC error is detected in a com-
mand string, all commands in the string,
up to and including the next X, are
ignored.

To correct the error condition, send only valid commands.
Refer to paragraph 5.9 for device-dependent command pro-
gramming details. An IDDC error is flagged in the U1 word,
as discussed in paragraph 5.9.20.

IDDCO (illegal device-dependent command option)
error

Sending the instrument a legal command with an illegal
option results in an IDDCO error.

For example, the command K9X has an illegal option (9) that
is not part of the instrument's programming language. Thus,
although the command K is valid, the option is not, and the
IDDCO error results.

NOTE

When an IDDCO error is detected in a
command string, all commands in the
string, up to and including the next X, are
ignored.

To correct this error condition, use only valid command
options, as discussed in paragraph 5.9. An error is flagged in
the U1 word, as discussed in paragraph 5.9.20.

Master/slave error

A master/slave error occurs when a communication or tim-
ing error is detected in the closed loop of units. If one or
more errors are detected, the error LED (ERR) is lit.

Table 5-5

IEEE-488 errors causing ERR LED to illuminate

Type of error

Description

Card ID error

IDDC

IDDCO

M/S error

Not in remote

Trigger before settling
time error
RAM fail

ROM fail

Setup error

Trig overrun

Power-up routine cannot iden-
tify one or more cards.
Illegal device-dependent com-
mand received.
Illegal device-dependent com-
mand option received.
Master/slave communication or
timing error.
X received while unit is in
LOCAL state.
Unit triggered before total set-
tling time expired.
Power-up routine or self-test
detected RAM error.
Power-up routine or self-test
detected program ROM check-
sum error.
Power-up routine detected
checksum errors in one or more
setups. (Affected setups are
cleared.)
Unit triggered before Ready bit
is set.